1. Field of the Invention
The present invention relates to a polyhydroxyalkanoate (hereinafter simply xe2x80x9cPHAxe2x80x9d) containing a novel structural unit and a production process thereof. More specifically, the present invention is directed to a process for producing a novel PHA containing a 3-hydroxyalkanoic unit which has a substituted phenylsulfinyl group and/or a substituted phenylsulfonyl group as a substituent at the end of its side chain, in which microorganisms capable of producing a PHA are cultured to produce and accumulate in the cell the PHA containing the 3-hydroxyalkanoic unit having the corresponding substituted phenylsulfanyl group as a substituent, and a sulfide-type sulfur in the PHA is selectively oxidized and converted into a sulfinyl or sulfonyl group, producing the desired PHA which is biodegradable.
This invention further relates to a charge control agent; a toner binder and a toner for developing electrostatic latent images, used in recording processes which utilize electrophotography, electrostatic recording, magnetic recording or the like, an image-forming method making use of the toner, and an image-forming apparatus therefor. More particularly, it relates to a charge control agent, a toner binder and a toner for developing electrostatic latent images, used in electrophotographic, electrostatic-recording and electrostatic-printing apparatus such as copying machines, printers and facsimile machines, an image-forming method making use of the toner, and an image-forming apparatus therefor. Still more particularly, it relates to a negatively charging charge control agent having higher safety for the human body and environment, a toner binder and a toner for developing electrostatic latent images, making use of such a charge control agent, an image-forming method making use of the toner, and an image-forming apparatus therefor.
2. Related Background Art
It has hitherto been reported that many microorganisms produce poly-3-hydroxybutyric acid (PHB) or other PHAs and accumulate it in the cell (xe2x80x9cHandbook of Biodegradable Plasticsxe2x80x9d, Biodegradable-Plastic Institute, K.K. N.T.S, pp.178-197, 1995). Like conventional plastics, these polymers can be utilized for the production of various products by melt processing or the like. Also, since they are biodegradable, they have an advantage of being completely broken down by microorganisms in the natural world, and by no means remain in natural environment to cause pollution unlike many conventional synthetic polymeric compounds. They also have superior adaptability to living bodies and are expected to be applicable as medical flexible members.
It is known that such PHAs produced by microorganisms may have various compositions and structures depending on types of microorganisms used for its production, the composition of culture medium, the conditions for culture and so forth. Researches on how to control such compositions and structures have hitherto chiefly been made from the viewpoint of the improvement in physical properties of PHAs.
(1) Biosyntheses of PHAs by the polymerization of a monomer unit having a relatively simple structure such as 3-hydroxybutyric acid (hereinafter simply xe2x80x9c3HBxe2x80x9d), include the following:
(a) Those which involve 3HB and 3-hydroxyvaleric acid (hereinafter xe2x80x9c3HVxe2x80x9d):
Japanese Patent Publications No. 6-15604, No. 7-14352, No. 8-19227, etc., and Japanese Patent Application Laid-Open No. 5-7492.
(b) Those which involve 3HB and 3-hydroxyhexanoic acid (hereinafter xe2x80x9c3HHxxe2x80x9d):
Japanese Patent Application Laid-Open No. 5-93049 and No. 7-265065.
(c) Those which involve 3HB and 4-hydroxybutyric acid (hereinafter xe2x80x9c4HBxe2x80x9d):
Japanese Patent Application Laid-Open No. 9-191893.
(d) Those which involve 3-hydroxyalkanoates having 6 to 12 carbon atoms:
Japanese Patent No. 2642937.
(e) Biosynthesis utilizing a single fatty acid as a carbon source. Products are substantially the same as those of (d); Appl. Environ. Microbiol., 58(2), 746, 1992.
All these are PHAs which are comprised of monomer units having an alkyl group in the side chain, i.e., xe2x80x9cusual PHAxe2x80x9d, and produced through xcex2-oxidation of hydrocarbons or synthesis of fatty acids from saccharides by the aid of microorganisms.
(2) When, however, broader application of such PHAs produced by microorganisms, e.g., application as functional polymers is taken into account, a PHA in which a substituent other than an alkyl group has been introduced in the side chain, i.e., xe2x80x9cunusual PHAxe2x80x9d is expected to be very useful. Examples of such a substituent may include those containing aromatic rings (such as a phenyl group and a phenoxy group), and unsaturated hydrocarbons, an ester group, an allyl group, a cyano group, halogenated hydrocarbons and epoxides. Of these, researches are enthusiastically made especially on PHAs having aromatic rings.
(a) Those which contain a phenyl group or a partially substituted phenyl group:
Macromol. Chem. Phys., 191, 1957-1965 (1990) and Macromolecules, 24, 5256-5260 (1991) report that Pseudomonas oleovorans produces a PHA containing 3-hydroxy-5-phenylvaleric acid as a unit, using 5-phenylvaleric acid as a substrate.
Macromolecules, 29, 1762-1766 (1996) reports that Pseudomonas oleovorans produces a PHA containing 3-hydroxy-5-(4xe2x80x2-tolyl)valeric acid as a unit, using 5-(4xe2x80x2-tolyl)valeric acid as a substrate.
Macromolecules, 32, 2889-2895 (1999) reports that Pseudomonas oleovorans produces a PHA containing 3-hydroxy-5-(2xe2x80x2, 4xe2x80x2-dinitrophenyl)valeric acid and 3-hydroxy-5-(4xe2x80x2-nitrophenyl)valeric acid as units, using 5-(2xe2x80x2, 4xe2x80x2-dinitrophenyl)valeric acid as a substrate.
(b) Those which contain a phenoxyl group or a partially substituted phenoxyl group:
Macromol. Chem. Phys., 195, 1665-1672 (1994) reports that Pseudomonas oleovorans produces a PHA copolymer of 3-hydroxy-5-phenoxyvaleric acid with 3-hydroxy-9-phenoxynonanoic acid, using 11-phenoxyundecanoic acid as a substrate.
Japanese Patent No. 2989175 discloses inventions which are concerned with a homopolymer comprised of 3-hydroxy-5-(monofluorophenoxy)pentanoate (3H5(MFP)P) units or 3-hydroxy-5-(difluorophenoxy)pentanoate (3H5(DFP)P) units, and a copolymer containing at least the (3H5(MFP)P) unit or the (3H5(DFP)P) unit; Pseudomonas putida capable of synthesizing such polymers; and processes for producing the above polymers by the use of the genus Pseudomonas. It is reported that, as the effect, a polymer having a phenoxyl group substituted at the side-chain terminal with 1 or 2 fluorine atom(s) can be synthesized by assimilating a long-chain fatty acid having a substituent and that stereo-regularity (isotacticity) and water repellency can be imparted while having a high melting point and retaining good processability.
In addition to such fluorine-substituted products, cyano-group- or nitro-group-substituted products are also being researched.
Can. J. Microbiol., 41, 32-43 (1995) and Polymer International, 39, 205-213 (1996) report that a PHA containing 3-hydroxy-p-cyanophenoxyhexanoic acid or 3-hydroxy-p-nitrophenoxyhexanoic acid as a monomer unit is produced using octanoic acid and p-cyanophenoxyhexanoic acid or p-nitrophenoxyhexanoic acid as a substrate by the use of Pseudomonas oleovorans strain ATCC 29347 and Pseudomonas putida strain KT 2442.
These reports are useful in order to obtain polymers which, differently from commonly available PHAs having an alkyl group in the side chain, all have an aromatic ring in the side chain, and have physical properties arising therefrom.
(3) Without being confined merely to changes in physical properties, research in a new category is being conducted to produce a PHA having a suitable functional group in the side chain.
For example, Macromolecules, 31, 1480-1486 (1996) and Journal of Polymer Science: Part A: Polymer Chemistry, 36, 2381-2387 (1998) report that a PHA containing at the side-chain terminal a unit having a vinyl group is synthesized, then the product synthesized is epoxidized with an oxidizing agent, thereby a PHA containing a highly reactive epoxy group at the side-chain terminal can be synthesized.
Besides the vinyl group, as an example of synthesizing a PHA containing a unit having a thioether (xe2x80x94Sxe2x80x94; a sulfanyl linkage), which is expected to provide a high reactivity, Pseudomonas putida strain 27N01 produces a PHA copolymer of 3-hydroxy-5-thiophenoxyvaleric acid (3-hydroxy-5-(phenylsulfanyl)valeric acid) with 3-hydroxy-7-thiophenoxyheptanoic acid (3-hydroxy-7-(phenylsulfanyl)heptanoic acid), using 11-thiophenoxyundecanoic acid (11-(phenylsulfanyl)undecanoic acid) as a substrate.
A number of methods are conventionally known as methods for electrophotography. In general, copied images are obtained by forming an electrostatic latent image on an image-bearing member (photosensitive member) by utilizing a photoconductive material and by various means, subsequently developing the latent image by the use of a toner to form a visible image (toner image), transferring the toner image to a transfer medium as the occasion demands, then fixing the toner image to the transfer medium by heating and/or pressing. As methods by which the electrostatic latent image is formed into a visible image, cascade development, magnetic brush development, pressure development and so forth are known in the art. Another method is also known in which, using a magnetic toner and a rotary developing sleeve provided with magnetic poles at the core, the magnetic toner is caused to fly from the developing sleeve to the photosensitive member by the aid of an electric field.
As development methods used when electrostatic latent images are developed, available are a two-component development method making use of a two-component type developer comprised of a toner and a carrier and a one-component development method making use of a one-component developer using no carrier and comprised of only a toner.
Fine colored particles commonly called a toner are composed of a binder resin and a colorant as essential components and optionally a magnetic material and so forth. In order to impart electric charges to the toner, the charging properties of the binder resin itself may be utilized without the use of any charge control agent, but the binder resin has poor charging stability with time and poor moisture resistance, hence a charge control agent is usually added for the purpose of charge retention and charge control of the toner.
Charge control agents nowadays known in the present technical field include, e.g., as negative charge control agents, azo dye metal complexes, metal complexes of aromatic dicarboxylic acids and metal complexes of salicylic acid derivatives. Also, known as positive charge control agents are Nigrosine dyes, triphenylmethane dyes, organotin compounds such as quaternary ammonium salt dibutyltin oxides of various types, and so forth. Toners containing any of as charge control agents, however, do not necessarily satisfy quality characteristics requisite for toner such as charging performance and stability with time in some cases.
For example, toners containing the azo dye metal complexes known as negative charge control agents are on a reasonable level in respect of the highness of charge quantity. However, since the azo dye metal complexes are crystal compounds with a low molecular weight, they may have a poor dispersibility depending on types of binder resins to be incorporated. In such a case, the negative charge control agents are not uniformly distributed in the binder resins, and the resultant toners also have a charge quantity distribution greatly lacking for sharpness, so that the images to be obtained may have a low gradation, showing a poor image formation performance. Moreover, the azo dye metal complexes have color tone specific thereto, and hence, under the existing conditions, they are used only in toners with hues limited mainly to black. When such toners are used as color toners, a serious problem arises in that they do not have the clearness necessary for producing images with enhanced color definition.
As examples of nearly colorless negative charge control agents, metal complexes of aromatic dicarboxylic acids are named, but may have a problem of low dispersibility because they are not perfectly colorless and they are crystal compounds with a low molecular weight.
As for the Nigrosine dyes and the triphenylmethane dyes, known as positive charge control agents, they stand colored in themselves, hence under the existing conditions, they are used only in toners with hues limited mainly to black. The toners containing such dyes may have poor stability over time when used in continuous copying. Conventional toners containing quaternary ammonium salts may insufficient moisture resistance, and may be so poor in stability over time as not to afford good images during repeated use.
In recent years, a worldwide discussion has emerged from the environmental conservation viewpoint concerning how waste should be curtailed and how the safety of waste should be improved; which is also applicable to the field of electrophotography. With the wide spread use of image-forming apparatus, the disposal of printed paper, waste toner and the like is increasing year by year, and the safety of such waste is also an important subject from the standpoint of global environmental conservation.
Taking into account such a point, studies are being made on polymer type charge control agents. They include compounds disclosed in, e.g., U.S. Pat. Nos. 4,480,021, 4,442,189 and 4,925,765 and Japanese Patent Application Laid-Open No. 60-108861, No. 61-3149, No. 63-38958 and No. 63-88564. In general, as polymer charge control agents used for toners exhibiting negative chargeability, there are frequently employed polymer compounds having ammonium salt type functional groups, such as copolymers of styrene and/or xcex1-methylstyrene with quaternary ammonium alkyl(meth)acrylates (Japanese Patent Application Laid-Open No. 8-220809, Japanese Patent Publication No. 8-3658, and Japanese Patent No. 2552133 and No. 2807796) and polyamide-modified polyester polymers using polyvalent amines as part of the structure of polyester resin composed of dicarboxylic units and glycol units (Japanese Patent Publication No. 4-46424). Such materials are advantageous in that they are colorless, but should be added in a large amount to ensure charge quantity, besides nitrogen atoms are thermally unstable and may be oxidized and heat-decomposed at the time of heat-kneading to cause a noxius odor or coloring.
In order to solve such problems, Japanese Patent Publication No. 7-120080 discloses positively chargeable polymer charge control agents composed of copolymers of phosphonium salts of vinylbenzyl halide. However, all these have a cationic functional group with a positive charge, hence apparently have moisture-absorption characteristics and thus is considered to have poor moisture resistance. In addition, a problem may arise in compatibility with binder resins which are basically nonionic.
Thus, these compounds do not have any sufficient performance as charge control agents, and have problems on charge quantity, charging-rise performance, stability with time, environmental stability and so forth. Considering not only the function but also influence on the human body, there is a strong desire to find a charge control agent which can be synthesized through safer and milder processes using safer compounds and smaller amounts of organic solvents.
From the viewpoint of environmental conservation, development is being made on resins degradable over time by the action of microorganisms, i.e., biodegradable resins. For example, as stated previously, it has been reported that many microorganisms are capable of producing the biodegradable resin PHA and accumulating it in the cell. It is known that such PHA can have various compositions and structures depending on types of microorganisms used for production, medium compositions, culture conditions and so forth. Researches have hitherto chiefly been made on how to control such compositions and structures from the viewpoint of the improvement in physical properties of PHA and have already gotten considerable achievement especially in the application to the field of materials for medical use. In the field of agriculture, too, the biodegradable resins are used in multifiles, gardening material and so forth, and also in sustained-release agricultural chemicals, fertilizers and so forth. Also in the field of leisure industry, the biodegradable resins are used in fishing lines, fishing articles, golf goods and so forth.
However, considering the wide spread application as plastics, under the existing conditions they can not still be said to be satisfactory in respect of physical properties. In order to make a PHA utilizable in a much wider range, it is important to more extensively study the improvement of physical properties. For that end, it is essential to research and development PHAs containing monomer units of various structures. The PHA of the type having a substituent introduced in its side chain can be expected to be expanded as a xe2x80x9cfunctional polymerxe2x80x9d having very useful functions and properties attributable to the properties of the substituent introduced, by selecting the substituent to be introduced according to the desired properties and so forth. Namely, it is also an important subject to research and develop such a PHA as can achieve both of such functionality and the biodegradability.
In the field of electrophotography, too, the application of biodegradable resins to binder resins is proposed especially in the production of toners. For example, U.S. Pat. No. 5,004,664 discloses a toner having as its composition a biodegradable resin, in particular, polyhydroxybutyric acid, polyhydroxyvaleric acid, or a copolymer or blend of these. Japanese Patent Application Laid-Open No. 6-289644 disclose an electrophotographic toner particularly used for heat-roll fixing, which is characterized in that at least a binder resin contains a vegetable wax and a biodegradable resin (as exemplified by polyesters produced by microorganisms and natural polymeric materials derived from vegetables or animals), and the vegetable wax is added to the binder resin in an amount of from 5 to 50% by weight.
Japanese Patent Application Laid-Open No. 7-120975 discloses an electrophotographic toner binder resin. Japanese Patent Application Laid-Open No. 9-274355 discloses a toner for developing electrostatic latent images which is characterized by containing a polyester resin and a colorant; the polyester resin being obtained by dehydration polycondensation of a composition containing lactic acid and a tri- or more functional oxycarboxylic acid.
Japanese Patent Application Laid-Open No. 8-262796 discloses an electrophotographic toner containing a binder resin and a colorant, and is characterized in that the binder resin comprises a biodegradable resin (as exemplified by aliphatic polyester resins) and the colorant comprises a water-insoluble coloring matter. Japanese Patent Application Laid-Open No. 9-281746 still also discloses a toner for developing electrostatic latent images which is characterized by containing a urethanated polyester resin and a colorant; the urethanated polyester resin being obtained by cross-linking polylactic acid with a tri- or more functional polybasic isocyanate.
In all the electrophotographic toners stated above, biodegradable resins are used as their binder resins, and they are understood to have the effect of contributing to environmental conservation.
However, no examples in which biodegradable resins are used in charge control agents have been reported and there is plenty of room for further contribution to environmental conservation.
Among these PHAs having a functional group in the side chain, taking notice of a PHA containing a 3-hydroxy-xcfx89-(phenylsulfanyl)alkanoic unit, its sulfide type sulfur (xe2x80x94Sxe2x80x94) is highly reactive, hence it is forecasted in the development of functional PHAs that studies are increasingly made on various derivatives of PHAs having the sulfide type sulfur (xe2x80x94Sxe2x80x94). However, so far there is only the aforementioned report on the biosynthesis of the PHA having an aromatic ring and a sulfide type sulfur (xe2x80x94Sxe2x80x94). In addition, The production process of the above PHA containing a 3-hydroxy-xcfx89-(phenylsulfanyl)alkanoic unit uses as a raw material xcfx89-(phenylsulfanyl)alkanoic acid whose carbon chain length is longer than that of units of the objective PHA, utilizes a xcex2 oxidation system in which the carbon chain is shortened two carbons by two carbons, and allows 3-hydroxyalkanoic acid having a carbon chain shorter than the raw material to be incorporated in the polymer unit, hence has such a problem that the polymer structure is difficult to control.
To solve the problem, the present inventors have already developed processes for producing PHAs primarily containing 3-hydroxy-xcfx89-(phenylsulfanyl)alkanoic units retaining the carbon chain length of xcfx89-(phenylsulfanyl)alkanoic acid as a raw material, the processes having been filed as Japanese Patent Application No. 2001-57145 and No. 2001-57142. These two applications disclose novel polyhydroxyalkanoates containing units having a sulfide (xe2x80x94Sxe2x80x94) structure in the side chain and efficient production process thereof. Specifically, the processes use microorganisms and produce PHA molecules which have a carbon chain corresponding to the raw material and a unit structure having in its terminal a phenylsulfanyl group or a substituted phenylsulfanyl group and in which a sulfide type sulfur with high reactivity (xe2x80x94Sxe2x80x94) is present. There is a strong desire for suggestions concerning means for converting from a structure containing the sulfide type sulfur with high reactivity (xe2x80x94Sxe2x80x94) to a useful PHA having different physicochemical properties by utilizing its reactivity and the novel PHA produced using the above noted means.
The present invention was made to solve the aforementioned problems and an object of the present invention is to provide, rather than the PHA containing a unit having a sulfide type sulfur (xe2x80x94Sxe2x80x94) in its side chain, a new PHA applicable to further wide spread use, specifically, a PHA with a new structure capable of improving physicochemical properties and a production process thereof. In particular, the present invention provides a novel PHA produced by using as an intermediate raw material a PHA mainly containing a 3-hydroxy-xcfx89-(phenylsulfanyl)alkanoic unit and/or a 3-hydroxy-xcfx89-(substituted phenylsulfanyl)alkanoic unit, which is produced by microorganisms, and converting its sulfide type sulfur (xe2x80x94Sxe2x80x94) to a group having another type of sulfur and a production process thereof.
Another object of the present invention is to provide a positively chargeable charge control agent which, as for its function, is more contributive to environmental conservation and has high performance (large charge quantity, quick rise of charging, superior stability over time, high environmental stability) and improved dispersibility, a toner binder containing the charge control agent, a static image developing toner containing the charge control agent, and an image forming method and an image forming apparatus using the static image developing toner.
As a result of enthusiastic research on the solution of the above problems, the present inventors found that when using as a raw material a PHA mainly containing a 3-hydroxy-xcfx89-(phenylsulfanyl)alkanoic unit and/or a 3-hydroxy-xcfx89-(substituted phenylsulfanyl)alkanoic unit, which is produced by microorganisms, and selectively oxidizing its sulfide type sulfur (xe2x80x94Sxe2x80x94) with a peroxide, the sulfide type sulfur is converted to a sulfonyl group (xe2x80x94SO2xe2x80x94) or a sulfinyl group (xe2x80x94SOxe2x80x94), and the resulting PHA has a novel structure and enhanced physicochemical properties. In addition, they found that instead of conducting the above oxidation treatment after allowing microorganisms to produce a PHA mainly containing a 3-hydroxy-xcfx89-(phenylsulfanyl)alkanoic unit and/or a 3-hydroxy-xcfx89-(substituted phenylsulfanyl)alkanoic unit as a intermediate material from xcfx89-(phenylsulfanyl)alkanoic acid and/or xcfx89-(substituted phenylsulfanyl)alkanoic acid as a raw material and once recovering the produced PHA through processes of separation and purification by solvent extraction, the oxidation also can be carried out using a peroxide after disrupting the cells and separating the PHA accumulated therein, thereby producing the objective PHA containing the unit having a sulfonyl group (xe2x80x94SO2xe2x80x94) and/or the unit having a sulfinyl group (xe2x80x94SOxe2x80x94). Based on the above findings, they brought the present invention to completion.
Therefore, the present invention provides a polyhydroxyalkanoate containing in its polymer molecule at least one unit of a 3-hydroxy-(substituted phenylsulfinyl)alkanoic acid unit of the general formula (1) below: 
(wherein R is H, halogen, CN, NO2, COORxe2x80x2 or SO2Rxe2x80x3 (where Rxe2x80x2 is H, Na, K, CH3 or C2H5, and Rxe2x80x3 is OH, ONa, OK, halogen atom, OCH3 or OC2H5) and x denotes any one of integers from 1 to 7 provided that it may take one or more different values in the polymer) and a 3-hydroxy-(substituted phenylsulfonyl)alkanoic acid unit of the general formula (2) below: 
(wherein R is H, halogen, CN, NO2, COORxe2x80x2 or SO2Rxe2x80x3 (where Rxe2x80x2 is H, Na, K, CH3 or C2H5 and Rxe2x80x3 is OH, ONa, OK, halogen atom, OCH3 or OC2H5) and x denotes any one of integers from 1 to 7 provided that it may take one or more different values in the polymer).
The polyhydroxyalkanoate according to the present invention may contain in the polymer molecule thereof not only at least one of the units of the general formulae (1) and (2), but also a 3-hydroxy-(substituted phenylsulfanyl)alkanoic unit of the general formula (3) below: 
(wherein R is H, halogen, CN, NO2, COORxe2x80x2 or SO2Rxe2x80x3 (where Rxe2x80x2 is H, Na, K, CH3 or C2H5 and Rxe2x80x3 is OH, ONa, OK, halogen, OCH3 or OC2H5) and x denotes any one of integers from 1 to 7 provided that it may take one or more different values in the polymer).
Further, the polyhydroxyalkanoate according to the present invention may contain in the polymer molecule thereof not only at least one of the units of the general formulae (1) and (2) and the unit of general formula (3), but also a 3-hydroxyalkanoic unit of the general formula (4) below: 
(wherein y denotes any one of integers from 0 to 8, provided that plural (y)s may take one or more values in the polymer) and/or a 3-hydroxyalk-5-enoic unit of the general formula (5): 
(wherein z denotes any one of integers from 3 and 5 provided that it may take one or more values in the polymer).
In the PHA of the above-mentioned structure, the polyhydroxyalkanoate may be composed of polymer molecules having a number average molecular weight within the range of 1,000 to 500,000. In the PHA of the present invention, its 3-hydroxyalkanoic acid unit has an asymmetric carbon atom at the 3-position, so that optical isomers exist. That is, the PHA of the present invention may take an R-form, S-form or racemi-form depending on the absolute configuration of the carbon atom at the 3-position. However, the use of the production process according to the present invention as described later on results in the same absolute configuration, specifically, the R-form that exhibits biodegradability for all the units and therefore is more preferable.
The PHA of the present invention in one aspect is a polyhydroxyalkanoate containing in the polymer molecule thereof at least one unit selected from the group consisting of a 3-hydroxy-5-(phenylsulfinyl)valeric acid unit of the chemical formula (6) below: 
and a 3-hydroxy-5-(phenylsulfonyl)valeric acid unit of the chemical formula (7) below: 
Here, the PHA may contain in the polymer molecule thereof a 3-hydroxy-5-(phenylsulfanyl)valeric acid unit of the chemical formula (8) below: 
in addition to the unit(s) of the chemical formulae (6) and/or (7) above.
The PHA of the present invention in still another aspect is a polyhydroxyalkanoate containing in the polymer molecule thereof at least one unit selected from the group consisting of a 3-hydroxy-4-(phenylsulfinyl)butyric acid unit of the chemical formula (9) below: 
and a 3-hydroxy-4-(phenylsulfonyl)butyric acid unit of the chemical formula (10) below: 
Here, the PHA may contain in the polymer molecule thereof a 3-hydroxy-4-(phenylsulfanyl)butyric acid unit of the chemical formula (11) below: 
in addition to the unit(s) of the chemical formulas (9) and/or (10) above.
The PHA of the present invention in still another aspect is a polyhydroxyalkanoate comprising in the polymer molecule thereof at least one unit selected from the group consisting of a 3-hydroxy-5-[(4-fluorophenyl)sulfinyl]valeric acid unit of the chemical formula (12) below: 
and a 3-hydroxy-5-[(4-fluorophenyl)sulfonyl]valeric acid unit of the chemical formula (13) below: 
Here, the PHA may contain in the polymer molecule thereof a 3-hydroxy-5-[(4-fluorophenyl)sulfanyl]valeric acid unit of the chemical formula (14) below: 
in addition to the unit(s) of the chemical formulas (12) and/or (13) above.
The PHA of the present invention in still another aspect is a polyhydroxyalkanoate containing the polymer molecule thereof at least one unit selected from the group consisting of a 3-hydroxy-5-[(3-fluorophenyl)sulfinyl]valeric acid unit of the chemical formula (15) below: 
and a 3-hydroxy-5-[(3-fluorophenyl)sulfonyl]valeric acid unit of the chemical formula (16) below: 
Here, the PHA may contain in the polymer molecule thereof a 3-hydroxy-5-[(3-fluorophenyl)sulfanyl]valeric acid unit of the chemical formula (17) below: 
in addition to the unit(s) of the chemical formulas (15) and/or (16) above.
Further, according to the present invention, there is also provided a method for producing the above-mentioned PHA of the present invention, that is, the invention relates to a method for producing a polyhydroxyalkanoate which has any one of the above-mentioned structures, comprising:
(Step 1) culturing a microorganism in a medium containing at least one xcfx89-(substituted phenylsulfanyl)alkanoic acid of a general formula (18) below: 
(wherein R is H, halogen, CN, NO2, COORxe2x80x2, or SO2Rxe2x80x3 (where Rxe2x80x2 is H, Na, K, CH3 or C2H5 and Rxe2x80x3 is OH, ONa, OK, halogen, OCH3 or OC2H5) and x denotes any one of integers from 1 to 7); and
(Step 2) treating a polyhydroxyalkanoate produced by the microorganism cultured in Step 1 with a peroxide compound.
In the method as described above, each of the units of the general formulae (1), (2) and (3) contained in the PHA have the relationships with the starting compounds of the general formula (18) as described below. First, the substituent R on the benzene ring of the starting compound of the general formula (18) is substantially retained as the substituent group R on the benzene ring of each unit of the general formulae (1), (2) or (3). Secondly, the units of the general formulas (1) and (2) are converted from the unit of the general formula (3) contained in the PHA prepared in Step 1 and the carbon numbers x of the side chains of the three units are identical with each other. Thirdly, the unit of the general formula (3) contained in the PHA prepared in Step 1 is produced by the process of xcex2-oxidation from the starting compound of the general formula (18) and the x in the unit of the general formula (3) is identical with the x in the unit of the general formula (18) or may in some cases be an integer smaller than the x in the general formula (18) by a multiple of 2 as xcex2-oxidation proceeds. Also, the x""s in the units of the general formulae (1) and (2), depending on the x in the unit of the general formula (3), are identical with the x in the unit of the general formula (18) or may in some cases be an integer smaller than the x in the unit of the general formula (18) by a multiple of 2.
In the method of producing PHA according to the present invention, it is preferable that the peroxide compound used in Step 2 is at least one peroxide compound selected from the group consisting of hydrogen peroxide, sodium percarbonate, metachloroperbenzoic acid, performic acid, and peracetic acid.
In the method of producing PHA, a step of separating the polyhydroxyalkanoate produced by the microorganism from the microbial cells cultured in Step 1 may be provided between Steps 1 and 2 above.
In addition, the production method of the present invention may comprise a step of disrupting microbial cells during the process of separating polyhydroxyalkanoate from the aforementioned microbial cells. In the step of disrupting the microbial cells, any method may be selected from a supersonic wave disrupting method, a homogenizer method, a bead impact method, a triturating method, a grinding method, and a freezing-thawing method as the means for disrupting the cells.
Alternatively, the method of the present invention may comprise a step of extracting polyhydroxyalkanoate from the microbial cells by using a solvent in which the polyhydroxyalkanoate is soluble during the process of separating polyhydroxyalkanoate from the microbial cells. Here, as the solvent in which polyhydroxyalkanoate is soluble, at least one solvent selected from chloroform, dichloromethane, dioxane, tetrahydrofuran, acetonitrile and acetone may be used.
On the other hand, in the method of producing PHA according to the present invention, it is preferable that the medium used in Step 1 contains polypeptone, and it is also preferable that the medium used in Step 1 contains yeast extract.
Alternatively, it is also preferable that the medium used in Step 1 contains a saccharide. In this case, it is more preferable that the saccharide contained in the medium is at least one compound selected from glyceraldehyde, erythrose, arabinose, xylose, glucose, galactose, mannose and fructose, alditols such as glycerol, erythritol and xylitol, aldonic acids such as gluconic acid, uronic acids such as glucuronic acid, galacturonic acid, disaccharides such as maltose, sucrose and lactose.
In addition, it is also preferable that the medium used in Step 1 contains an organic acid or its salt. In this case, it is preferable that the organic acid or its salt contained in the medium is at least one compound selected from pyruvic acid, malic acid, lactic acid, citric acid, succinic acid, and salts thereof.
Also, it is preferable the medium used in Step 1 contains an amino acid or its salt. In this case, it is desirable that the amino acid or its salt contained in the medium is at least one compound selected from glutamic acid, aspartic acid and salts thereof.
In addition, the medium used in Step 1 may contain a linear alkanoic acid having 4 to 12 carbon atoms or its salt.
In the method of producing PHA according to the present invention, the culture of the microorganism in Step 1 can be performed by a culture method having at least two stages comprising:
(Step 1-1) culturing the microorganism in a medium containing at least one xcfx89-(substituted phenylsulfanyl)alkanoic acid of the general formula (18) above and polypeptone; and subsequently
(Step 1-2) further culturing the microorganism cultured in Step 1-1 above in a medium containing at least one xcfx89-(substituted phenylsulfanyl)alkanoic acid of the general formula (18) above and an organic acid or salt thereof. Also, in this case, it is preferable that the organic acid or its salt contained in the medium used in Step 1-2 above is at least one compound selected from pyruvic acid, malic acid, lactic acid, citric acid, succinic acid, and salts thereof.
In the method of producing PHA according to the present invention, it is possible that the culture of the microorganism in Step 1 is performed by a culture method having at least two stages comprising:
(Step 1-3) culturing the microorganism in a medium containing at least one xcfx89-(substituted phenylsulfanyl)alkanoic acid of the general formula (18) above and a saccharide; and subsequently
(Step 1-4) further culturing the microorganism cultured in Step 1-3 above in a medium containing at least one xcfx89-(substituted phenylsulfanyl)alkanoic acids of the general formula (18) above and a saccharide. In this case, it is preferable that the saccharide contained in the medium used in Step 1-3 and Step 1-4 above is at least one compound selected from glyceraldehyde, erythrose, arabinose, xylose, glucose, galactose, mannose and fructose, alditols such as glycerol, erythritol and xylitol, aldonic acids such as gluconic acid, uronic acids such as glucuronic acid, galacturonic acid, disaccharides such as maltose, sucrose and lactose.
When employing the aforementioned two-stage culture step, the medium used in the second-stage culture step, specifically Steps 1-2 and 1-4 above, preferably contains no nitrogen source. That is, when a production method is used in which two or more culture steps are provided in Step 1, the productivity of PHA by the microorganism can be improved by controlling the nitrogen source in the medium used in a later-stage culture step, for example, a second stage culture step. The method for the production of PHA according to the present invention in one aspect may be a method of producing a polyhydroxyalkanoate containing in the polymer molecule thereof at least one unit selected from a 3-hydroxy-5-(phenylsulfinyl)valeric acid unit of the chemical formula (6) below: 
and a 3-hydroxy-5-(phenylsulfonyl)valeric acid unit of the chemical formula (7) below: 
and optionally a 3-hydroxy-5-(phenylsulfanyl)valeric acid unit of the chemical formula (8) below: 
where the method comprises culturing a microorganism in a medium containing 5-(phenylsulfanyl)valeric acid of the chemical formula (19): 
and treating the polyhydroxyalkanoate produced by the cultured microorganism with at least one peroxide compound selected from hydrogen peroxide, sodium percarbonate, metachloroperbenzoic acid, performic acid, and peracetic acid.
In addition, the method for the production of PHA according to the present invention in one aspect may be a method of producing a polyhydroxyalkanoate containing in the polymer molecule thereof at least one unit selected from a 3-hydroxy-4-(phenylsulfinyl)butyric acid unit of the chemical formula (9) below: 
and a 3-hydroxy-4-(phenylsulfonyl)butyric acid unit of the chemical formula (10) below: 
and optionally a 3-hydroxy-4-(phenylsulfanyl)butyric acid unit of the chemical formula (11) below: 
where the method comprises culturing a microorganism in a medium containing 4-(phenylsulfanyl)butyric acid of the chemical formula (20): 
and treating the polyhydroxyalkanoate produced by the cultured microorganism with at least one peroxide compound selected from hydrogen peroxide, sodium percarbonate, metachloroperbenzoic acid, performic acid, and peracetic acid.
Further, the method for the production of PHA according to the present invention in one aspect may be a method of producing a polyhydroxyalkanoate containing in the polymer molecule thereof at least one unit selected from a 3-hydroxy-5-[(4-fluorophenyl)sulfinyl]valeric acid unit of the chemical formula (12) below: 
and a 3-hydroxy-5-[(4-fluorophenyl)sulfonyl]valeric acid unit of the chemical formula (13) below: 
and optionally a 3-hydroxy-5-[(4-fluorophenyl)sulfanyl]valeric acid unit of the chemical formula (14) below: 
where the method comprises culturing a microorganism in a medium containing 5-[(4-fluorophenyl)sulfanyl]valeric acid of the chemical formula (21): 
and treating the polyhydroxyalkanoate produced by the cultured microorganism with at least one peroxide compound selected from hydrogen peroxide, sodium percarbonate, metachloroperbenzoic acid, performic acid, and peracetic acid.
Still further, the method for the production of PHA according to the present invention in one aspect may be a method of producing a polyhydroxyalkanoate containing in the polymer molecule thereof at least one unit selected from the group consisting of a 3-hydroxy-5-[(3-fluorophenyl)sulfinyl]valeric acid unit of the chemical formula (15) below: 
and a 3-hydroxy-5-[(3-fluorophenyl)sulfonyl]valeric acid unit of the chemical formula (16) below: 
and optionally a 3-hydroxy-5-[(3-fluorophenyl)sulfanyl] valeric acid unit of the chemical formula (17) below: 
wherein the method comprises culturing a microorganism in a medium containing 5-[(3-fluorophenyl)sulfanyl]valeric acid of the chemical formula: 
and treating the polyhydroxyalkanoate produced by the cultured microorganism with at least one peroxide compound selected from hydrogen peroxide, sodium percarbonate, metachloroperbenzoic acid, performic acid, and peracetic acid.
In the method of producing PHA according to the present invention, it is preferable that the microorganism producing a polyhydroxyalkanoate in Step 1 is a microorganism belonging to the genus Pseudomonas. Here, for example, it is more preferable that the microorganism belonging to the genus Pseudomonas is selected from Pseudomonas cichorii strain YN2 (FERM BP-7375), Pseudomonas cichorii strain H45 (FERM BP-7374), and Pseudomonas jessenii strain P161 (FERM BP-7376).
Further, the present inventors have made intensive studies to develop a charge control agent which exhibits high performance and is substantially colorless and finally reached the present invention.
Thus, according to the present invention, there is provided a charge control agent containing at least one unit of monomer units represented by the general formulae (1) and (2) below: 
(wherein R is H, halogen, CN, NO2, COORxe2x80x2, or SO2Rxe2x80x3 (where Rxe2x80x2 represents any one of H, Na, K, CH3 and C2H5 and Rxe2x80x3 represents any one of OH, ONa, OK, halogen, OCH3 and OC2H5) and x is an integer and may take one or more values within the range indicated in the chemical formula).
The PHA contained in the charge control agent according to the present invention, may contain, in addition to at least one of the units of chemical formulae (1) and (2), a unit of a chemical formula (3) below: 
(wherein R is H, halogen, CN, NO2, COORxe2x80x2, or SO2Rxe2x80x3 (where Rxe2x80x2 represents any one of H, Na, K, CH3 or C2H5 and Rxe2x80x3 represents any one of OH, ONa, OK, halogen, OCH3 or OC2H5) and x is any integer and may take one or more values within the range indicated in the chemical formula).
The PHA contained in the charge control agent according to the present invention may contain, in addition to at least one of the units of chemical formulae (1)and (2) and the unit of formula (3), at least one of units of chemical formulae (4) and (5) below: 
(wherein y and z are each an integer and may take one or more values independently of the units of the formulae (1), (2) and (3) within the range indicated in the chemical formula):
The polyhydroxyalkanoate contained in the charge control agent according to the present invention has a number average molecular weight in the range from 1,000 to 500,000.
In addition, the present invention relates to a toner binder containing the charge control agent of the present invention.
Further, the present invention relates to an electrostatic charge image developing toner containing at least a binder resin, a colorant and the charge control agent.
Also, the present invention relates to an image forming method including at least the steps of externally applying a voltage to a charging member to charge an electrostatic latent image bearing member, developing the electrostatic charge image by using an electrostatic charge image developing toner to form a toner image on the electrostatic latent image bearing member, transferring the toner image on the electrostatic latent image bearing member to a recording medium, and thermally fixing the toner image on the recording medium, wherein the electrostatic charge image developing toner containing at least a binder resin, a colorant and the charge control agent, is used.
Further, the present invention relates to an image forming method including at least the steps of externally applying a voltage to a charging member to charge an electrostatic latent image bearing member, forming an electrostatic charge image on the charged electrostatic latent image bearing member, developing the electrostatic charge image by using an electrostatic charge image developing toner to form a toner image on the electrostatic latent image bearing member, transferring the toner image on the electrostatic latent image bearing member to an intermediate transfer member in a first stage, transferring the toner image on the intermediate transfer member to a recording medium in a second stage, and thermally fixing the toner image on the recording medium thereto, wherein the electrostatic charge image developing toner containing at least a hinder resin, a colorant and the charge control agent, is used.
Also, the present invention relates to an image forming apparatus having at least a means for externally applying a voltage to a charging member to charge an electrostatic latent image bearing member, a means for forming an electrostatic charge image on the charged electrostatic latent image bearing member, a developing means for developing the electrostatic charge image by using an electrostatic charge image developing toner to form a toner image on the electrostatic latent image bearing member, a transfer means for transferring the toner image on the electrostatic latent image bearing member to a recording medium, and a fixing means for thermally fixing the toner image on the recording medium, wherein the electrostatic charge image developing toner containing at least a binder resin, a colorant and the charge control agent, is used.
Furthermore, the present invention relates to an image forming apparatus having at least a means for externally applying a voltage to a charging member to charge an electrostatic latent image bearing member, a means for forming an electrostatic charge image on the charged electrostatic latent image bearing member, a developing means for developing the electrostatic charge image by using an electrostatic charge image developing toner to form a toner image on the electrostatic latent image bearing member, a first transfer means for transferring the toner image on the electrostatic latent image bearing member to an intermediate transfer member, a second transfer means for transferring the toner image on the intermediate transfer member to a recording medium, and a fixing means for thermally fixing the toner image on the recording medium, wherein the electrostatic charge image developing toner containing at least a binder resin, a colorant and the charge control agent, is used.
The method for the production of PHA according to the present invention makes it possible to produce a novel, biodegradable polyhydroxyalkanoate containing at least one unit having a phenylsulfinyl group or phenylsulfonyl group on the side chain thereof by cultivating a microorganism in a medium containing a xcfx89-(phenylsulfanyl)alkanoic acid or a xcfx89-(substituted phenylsulfanyl)alkanoic acid and treating the PHA containing a 3-hydroxy-(phenylsulfanyl)alkanoic acid unit or a 3-hydroxy-(substituted phenylsulfanyl)alkanoic acid unit produced by the microorganism with a peroxide compound to convert the sulfanyl group (xe2x80x94Sxe2x80x94) into a sulfinyl group (xe2x80x94SOxe2x80x94) or a sulfonyl group (xe2x80x94SO2xe2x80x94). The obtained PHA can be so made as to be an intermediate raw material, i.e., a PHA in which a 3-hydroxy-(phenylsulfanyl)alkanoic acid unit or a 3-hydroxy-(substituted phenylsulfanyl)alkanoic acid unit derived from a PHA containing a 3-hydroxy-(phenylsulfanyl)alkanoic acid unit or a 3-hydroxy-(substituted phenylsulfanyl)alkanoic acid unit produced by the cultured microorganism partially remains, by controlling the conditions of treatment with the peroxide compound. In addition, the PHA production method according to the present invention can regulate the content ratio of the three units having respectively the phenylsulfinyl group, phenylsulfonyl group and phenylsulfanyl group on the side chains thereof with high reproducibility by controlling the conditions of treatment with peroxide compound and the resulting PHA can be utilized as a useful polyhydroxyalkanoate having new characteristics.
Further, according to the present invention, the addition of at least one compound shown above as charge control agents to an electrostatic charge image developing toner composition can provide an electrostatic charge image developing toner which has excellent charging properties, improved dispersibility of compounds in a toner resin and improved spent properties and which causes no fogging of images and is excellent in transferability at the time of output in an image forming apparatus and is highly suited for electrophotographic processes. Furthermore, the charge control agent used in the present invention is also characterized in that it is colorless or only slightly colored so that any desired coloring agent may be selected depending on the color tone required for color toners and it does not impair at all the color tone that the dye or pigment inherently has. In addition, the electrostatic charge image developing toner of the present invention does not require incineration treatment since it is biodegradable so that it is significantly advantageous to industry in light of prevention of air pollution and global warming.
The above and other objects, effects, features and advantages of the present invention will become more apparent from the following description of embodiments thereof taken in conjunction with the accompanying drawings.